PROJECT SUMMARY The proposed K23 Career Development Award will enable Jennifer Woo Baidal, MD, MPH to establish an independent research career with expertise in childhood obesity and pediatric nonalcoholic fatty liver disease (NAFLD). Dr. Woo Baidal is a pediatric gastroenterologist whose long-term goal is to translate epidemiologic and patient-oriented research findings to interventions to reduce childhood obesity and NAFLD in vulnerable populations, but further training is required to accomplish this goal. Thus, she has assembled a team of mentors to fulfill her immediate goal for advanced training in (1) diagnostic research principles in relation to pediatric NAFLD; (2) epidemiologic research including cohort design and implementation; (3) quantitative research including longitudinal data analysis; (4) genetic and genomic research; and (5) research dissemination and professional development. Pediatric NAFLD is a serious complication of childhood obesity and the most common chronic pediatric liver disease worldwide. NAFLD comprises a spectrum of phenotypes including hepatic steatosis, nonalcoholic steatohepatitis (NASH), and fibrosis/cirrhosis. Until recently, a major barrier to advancing understanding of risk factors for pediatric NAFLD has been lack of non-invasive diagnostic modalities that are practical in children. Transient elastography is a FDA-approved, non-invasive tool that simultaneously measures hepatic steatosis and fibrosis at the point-of-care, and is widely used in adults to monitor disease progression and treatment response. The candidate?s preliminary research supports the ability of transient elastography to diagnosis steatosis and fibrosis in children, thus allowing longitudinal studies of the emergence and progression of pediatric NAFLD in children with overweight and obesity. The proposed research consists of two inter-related aims to (1) complete a full-scale validation study for transient elastography in a pediatric setting and (2) use transient elastography to test specific dietary, behavioral, and biologic hypotheses related to etiology and progression of NAFLD in childhood. This research will leverage two existing cohorts at Columbia University Medical Center and will establish a cohort of 400 children at risk for NAFLD as a platform for future R01 applications. Successful completion of this project will shed new light on mechanisms that lead to development of pediatric NAFLD in children with overweight/obesity, and provide Dr. Woo Baidal the necessary training and experience to develop an independent research program focused on reduction of pediatric NAFLD in the context of childhood obesity.